Obliquity-Driven CO2 Exchange Between Mars' Atmosphere, Regolith, and Polar Cap

Discerning the total mass of Mars' obliquity-timescale (similar to 10(5)-year) exchangeable CO2 inventory has been elusive for decades due to the unknown adsorptive capacity of its regolith. Now, however, the stratigraphy of Mars' recently discovered South Polar Massive CO2 Ice Deposit (MCID) provides a record of orbit-driven CO2 exchange between its polar cap, atmosphere, and regolith with sufficient constraint to calculate the adsorptive capacity of its regolith and therefore the total mass of its exchangeable CO2 inventory. We use a numerical climate model and Markov Chain Monte Carlo analysis to show that the observed MCID stratigraphic record is most consistent with a mobile CO2 inventory of 3.8-1.2+3.0x1017 kg (100-34+80 mbar, 68% confidence interval) that exchanges on obliquity timescales. We find that adsorptive CO2 exchange with the regolith on obliquity timescales likely occurs in the depth range of >similar to 200 m to

Automated summary

Researchers have successfully calculated the adsorptive capacity of Martian regolith and the total mass of its exchangeable CO2 by analyzing the recently discovered South Polar Massive CO2 Ice Deposit. The study shows the existence of a mobile CO2 inventory on obliquity timescales.